title: Arabidopsis heterotrimeric G protein β subunit, AGB1, regulates brassinosteroid signalling independently of BZR1.
abstract: The Arabidopsis thaliana heterotrimeric G protein β subunit, AGB1, is involved in both abscisic acid (ABA) signalling and brassinosteroid (BR) signalling, but it is unclear how AGB1 regulates these signalling pathways. A key transcription factor downstream of BR, BZR1, and its gain-of-function mutant, bzr1-1, were overexpressed in an AGB1-null mutant, agb1-1, to examine their effects on the BR hyposensitivity and the ABA hypersensitivity of agb1-1, and to examine whether AGB1 regulates the functions of BZR1. Because the amino acid sequence of AGB1 contains 17 putative modification motifs of glycogen synthase kinase 3/SHAGGY-like protein kinases (GSKs), which are known components of BR signalling, the interaction between AGB1 and one of the Arabidopsis GSKs, BIN2, was examined. Expression of bzr1-1 alleviated the effects of a BR biosynthesis inhibitor, brassinazole, in both the wild type and agb1-1, and overexpression of BZR1 alleviated the effects of ABA in both the wild type and agb1-1. AGB1 did not affect the phosphorylation state of BZR1 in vivo. AGB1 interacted with BIN2 in vitro, but did not affect the phosphorylation state of BIN2. The results suggest that AGB1 interacts with BIN2, but regulates the BR signalling in a BZR1-independent manner.
authors.affiliation: Asian Natural Environmental Science Center, The University of Tokyo, 1-1-1 Midori-cho, Nishitokyo-shi, Tokyo 188-0002, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Tsugama
authors.forename: Shenkui
authors.initials: S
authors.lastname: Liu
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Takano
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D060406:Brassinosteroids / Q000378:metabolism*; D004268:DNA-Binding Proteins; D044387:GTP-Binding Protein beta Subunits / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D014230:Triazoles / Q000494:pharmacology; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; D060406:Brassinosteroids; D004268:DNA-Binding Proteins; D044387:GTP-Binding Protein beta Subunits; D009687:Nuclear Proteins; D011494:Protein Kinases; D014230:Triazoles; C089590:AGB1 protein, Arabidopsis; C454444:BZR1 protein, Arabidopsis; C448985:At4g18710 protein, Arabidopsis; C412342:brassinazole
keywords: Abscisic acid; Arabidopsis thaliana; brassinosteroid; glycogen synthase kinase 3/SHAGGY-like protein kinase; heterotrimeric G protein β subunit; protein–protein interaction.